Design of meso-structured titanium oxo based hybrid organic–inorganic networks

Soler-Illia, Galo J. A. A.; Scolan, Emmanuel; Louis, Audrey; Albouy, Pierre‐Antoine; Sanchez, C.

doi:10.1039/b006139p

Cited by 145 publications

(129 citation statements)

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“…2). The wormhole-like mesostructure is not induced by micelles but by the interaction of nanosized Ti-O particles with amphiphilic surfactant molecules as proposed by Sanchez and co-workers [15,16] and Ozin and co-workers. [31] In conclusion, mesoporous titania materials with a hierarchical interior macroporous structure have been synthesized in a one-step simple chemical synthesis in the presence of poly(ethylene oxide) surfactant.…”

mentioning

confidence: 88%

“…The partially formed hydrolyzed alkoxides (titanium oxo cluster or nanosized Ti-O particles, denoted as Ti w O x (OH) y (OR) z , [31] with weak hydrophobic character though having some titanol TiOH groups on the surface) are allowed to interact with amphiphilic surfactant molecules, forming a worm-like mesotextured hybrid phase of nanoparticles. [15,16,31] Simultaneously the hydrophobic, partially hydrolyzed titanium alkoxide can act as the oil component in the water±alcohol±surfactant solution to form a water-in-oil microemulsion during the early re- action stage. The PEO surfactants also play an important role in the stabilization of the microemulsion droplets.…”

mentioning

confidence: 99%

“…Phosphorus-free mesoporous titania materials have been recently synthesized by various methods using neutral primary amines, [8,9] cationic alkyl trimethylammonium surfactants, [10±12] or non-ionic poly(ethylene oxide) (PEO)-based surfactants [13,14] as structure-directing agents. Sanchez and co-workers [15,16] investigated the interactions between PEO-based templates and metallic centers in alkoxide/alcohol/water/HCl mixtures and stressed the role of water in the mesoscopic organization. Mesoporous metal oxide molecular sieves with macroporous structures are of considerable interest as potential catalysts and sorbents, partly because the textural mesopores and intrinsic interconnected pore systems of macrostructures should efficiently transport guest species to framework binding sites.…”

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Hierarchically Mesostructured Titania Materials with an Unusual Interior Macroporous Structure

Yuan

Ren

Su³

2003

Advanced Materials

138

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Since the discovery of silica-based mesophases, [1] the surfactant-templated synthesis method based on the hydrolysis and crosslinking of inorganic precursors at the surfaces of supramolecular surfactant assemblies has been extended to prepare a variety of mesostructures. Much effort has been made to synthesize ordered mesoporous transition metal oxides because of their enormous potential in the fields of electromagnetics, photoelectronics, catalysis, and separation.[2±4] Titanium oxide is an extremely interesting material because of its multiple applications, for example, photocatalysis and catalyst support. Although mesoporous TiO 2 , with high surface area and narrow pore size distribution, has been synthesized by a modified sol-gel route with phosphate surfactants, [5±7] a significant amount of phosphorus remained after calcination, and these remaining phosphorus species will poison the surface catalytic sites. Phosphorus-free mesoporous titania materials have been recently synthesized by various methods using neutral primary amines, [8,9] cationic alkyl trimethylammonium surfactants, [10±12] or non-ionic poly(ethylene oxide) (PEO)-based surfactants [13,14] as structure-directing agents. Sanchez and co-workers [15,16] investigated the interactions between PEO-based templates and metallic centers in alkoxide/alcohol/water/HCl mixtures and stressed the role of water in the mesoscopic organization. Mesoporous metal oxide molecular sieves with macroporous structures are of considerable interest as potential catalysts and sorbents, partly because the textural mesopores and intrinsic interconnected pore systems of macrostructures should efficiently transport guest species to framework binding sites. Micromoulding methods using emulsion droplets, latex spheres, or bacterial threads have been used recently to prepare ordered inorganic structures with pore sizes in the submicrometer or micrometer range.[17±23] These techniques have been extended to the fabrication of oxide materials with macro-mesoporous structures by combination with surfactant templating methods. [20±23] However, the preparation of hierarchically ordered structures of multiple pores in a single body, such as seen in diatoms in nature, still remains an experimental challenge.[23] Sponge-like silica membranes with three-dimensional (3D) meso-macrostructures have been synthesized from an electrolyte phase of block copolymer/silica systems, although inorganic salt crystals inevitably co-grew with the silica membrane.[24] Antonelli [25] reported the synthesis of macro-mesoporous niobium oxides by a ligand-assisted vesicle templating strategy; the addition of an amount of NaCl in a niobium ethoxide/amine gel was necessary. In this communication, we describe a new method for the synthesis of mesoporous titania materials with an unusual macroporous structure. A non-ionic poly(alkylene oxide) surfactant was used as a template in the synthesis of mesoporous titania materials. An inorganic precursor Ti(OPr) 4 was mixed with an ethanol solution of C 16 (EO) ...

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confidence: 88%

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confidence: 99%

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confidence: 99%

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Hierarchically Mesostructured Titania Materials with an Unusual Interior Macroporous Structure

Yuan

Ren

Su³

2003

Advanced Materials

138

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“…Above 380 C, the mass loss appears negligible. Based on this TGA trace and several related papers, [14,16,26,29,31] the as-synthesized thick films were correspondingly calcined in either of two conditions: 350 C/4 h, the usual calcination condition for completely removing templates …”

Section: Polarization Optical Microscopymentioning

confidence: 99%

“…The initial acidic conditions, which are subsequently eliminated by evaporation of the acid, provide a means for readily controlling the polymerization of the inorganic network. Additionally, this approach provides significant flexibility in processing, allowing for the preparation of mesostructured ªbulkº gels, [13,16,26,29,30] thin films, [14,19,31±35] and fibers, [36] in addition to powdered forms of the material.…”

Section: Introductionmentioning

confidence: 99%

Thermally Stable Two‐Dimensional Hexagonal Mesoporous Nanocrystalline Anatase, Meso‐nc‐TiO₂: Bulk and Crack‐Free Thin Film Morphologies

Choi

Mamak

Coombs

et al. 2004

Adv Funct Materials

362

307

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Herein a novel synthetic route is described for the production of thermally stable, structurally well‐defined two‐dimensional (2D) hexagonal mesoporous nanocrystalline anatase (meso‐nc‐TiO2), with a large pore diameter, narrow pore‐size distribution, high surface area, and robust inorganic walls comprised of nanocrystalline anatase. The synthetic approach involves the evaporation‐induced co‐assembly of a non‐ionic amphiphilic triblock‐copolymer template and titanium tetraethoxide, but with a pivotal change in the main solvent of the system, where the commonly used ethanol is replaced with 1‐butanol. This seemingly minor modification in solvent type from ethanol to 1‐butanol turns out to be the key synthetic strategy for achieving a robust, structurally well‐ordered meso‐nc‐TiO2 material in the form of either thick or thin films. The beneficial “solvent” effect originates from the higher hydrophobicity of 1‐butanol than ethanol, enhancing microphase separation and templating, lower critical micelle concentration of the template in 1‐butanol, and the ability to increase the relative concentration of the inorganic precursor to template in the co‐assembly synthesis. Moreover, thin films with dimensions of several centimeters that are devoid of cracks down to the length scale of the mesostructure itself, having high porosity, well‐defined mesostructural features, and semi‐crystalline pore walls were straightforwardly and reproducibly obtained as a result of the physicochemical property advantages of 1‐butanol over ethanol within our synthesis scheme.

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Ordered Mesoporous Materials

Kleitz

2008

Handbook of Heterogeneous Catalysis

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2 State of the art access to the controlled generation of well-defined polymolecular architectures in layers, films, membranes, micelles, gels or mesophases. 26 The generation of ordered mesoporous materials is possible via templating by self-assembled liquid-crystalline phases. In this case, there is a geometrical correlation between the surfactants array size and shape and the final pore size and geometry in the mesophase. Surfactants consist of a hydrophilic part, e.g. ionic, non-ionic, zwitterionic or polymeric groups, often called the "head" and a hydrophobic part, the "tail", e.g. alkyl or polymeric chains. This amphiphilic character enables surfactants molecules to associate in supramolecular micellar arrays. 27 Single amphiphile molecules tend to form aggregates in aqueous solution due to hydrophobic effects. Above a certain critical concentration of amphiphiles, formation of an assembly, such as a spherical micelle, is favored. In these aggregates, * the surfactant molecules are arranged such that the heads form the outer surface facing the water and the tails are clustered together pointing toward the center. The formation of micelles, the shape of the micelles, and the aggregation of the micelles into liquid crystals depend on the surfactant concentration. At very low concentration, the surfactant is present as free molecules dissolved in solution and adsorbed at interfaces. At slightly higher concentration, called the critical micelle concentration, CMC, the individual molecules form small spherical aggregates. At higher concentrations, CMC2, spherical micelles eventually coalesce to form elongated cylindrical rod-like micelles. CMC2 depends strongly on temperature, surfactant chain length and surfactant counter-anion binding strength. With increasing concentrations, liquid crystalline phases (LC) form. Initially, the rod-like micelles aggregate in hexagonal close-packed arrays. As the concentration increases further, cubic phases form followed by lamellar phases. 23,27 Details of this sequence might vary, depending on the surfactant, but in general the sequences is valid for most systems.Efficient template removal and faithful imprinting have been largely shown to depend on the nature of the interactions between the template and the embedding matrix, and the ability of the matrix to adapt to the template. The intimate template-matrix association required for supramolecular templating of inorganic mesophases is generally facilitated by the flexibility of amorphous inorganic networks with low structural constrains, small inorganic oligomers, and by the large radius of curvature of the organic template. Ideally, after removal of the core molecules from the surrounding matrix the shape of the voids that remain reflects the shape of the template. * The term aggregate is used for the supramolecular array formed upon self-assembly of single surfactant molecule.

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Design of meso-structured titanium oxo based hybrid organic–inorganic networks

Cited by 145 publications

References 48 publications

Hierarchically Mesostructured Titania Materials with an Unusual Interior Macroporous Structure

Hierarchically Mesostructured Titania Materials with an Unusual Interior Macroporous Structure

Thermally Stable Two‐Dimensional Hexagonal Mesoporous Nanocrystalline Anatase, Meso‐nc‐TiO₂: Bulk and Crack‐Free Thin Film Morphologies

Ordered Mesoporous Materials

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Design of meso-structured titanium oxo based hybrid organic–inorganic networks

Cited by 145 publications

References 48 publications

Hierarchically Mesostructured Titania Materials with an Unusual Interior Macroporous Structure

Hierarchically Mesostructured Titania Materials with an Unusual Interior Macroporous Structure

Thermally Stable Two‐Dimensional Hexagonal Mesoporous Nanocrystalline Anatase, Meso‐nc‐TiO2: Bulk and Crack‐Free Thin Film Morphologies

Ordered Mesoporous Materials

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Thermally Stable Two‐Dimensional Hexagonal Mesoporous Nanocrystalline Anatase, Meso‐nc‐TiO₂: Bulk and Crack‐Free Thin Film Morphologies